Ground fault circuit interrupters are widely used in some installations as required by OSHA and the National Electric Code. The Underwriters' Laboratories, Inc. has established the performance standard for Class A ground fault circuit interrupters as having trip level of no more than 5 milliamperes within an equated and established period of time. Thus "the duration in time of ground fault shock should be limited to be within the range of normal human endurance".
The need for testing circuit interrupters has been established by testing a substantial number of them and in some instances there have been failures to trip at all, with others tripping occurred at too low or too high a milliampere reading or trips occured after a prolonged period of time, and in some instances their operation was too erratic. If ground fault circuit interrupters do not perform as specified they obviously present unsafe hazardous conditions to personnel.
Testing equipment is presently available but as far as I am aware these provide information as to leakage current only in terms of milliamperes. My testing of Class A interrupters has resulted in finding instances where, while the milliampere readings are within the specified range, there is a wide range of deviations of tripping time in terms of milliseconds, in some cases, in a clearly unsafe range. As far as I am aware, there are no references pertinent to this invention.